Method for forming semiconductor device structure with conductive line

ABSTRACT

A method for forming a semiconductor device structure is provided. The method includes forming a first mask layer over a dielectric layer. The method includes forming a second mask layer over a first top surface of the first mask layer, the inner wall, and the bottom surface. The method includes removing the second mask layer covering the bottom surface to form a second trench in the second mask layer. The method includes forming an anti-bombardment layer over a second top surface of the second mask layer. The second mask layer and the anti-bombardment layer are made of different materials. The method includes removing the first portion, the first mask layer, the second mask layer, and the anti-bombardment layer to form a third trench in the dielectric layer. The method includes forming a conductive structure in the third trench.

PRIORITY CLAIM AND CROSS-REFERENCE

This Application claims the benefit of U.S. Provisional Application No.62/583,121, filed on Nov. 8, 2017, the entirety of which is incorporatedby reference herein.

This application is a Divisional of U.S. application Ser. No.15/884,760, filed on Jan. 31, 2018, the entirety of which isincorporated by reference herein.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. Technological advances in IC materials and design have producedgenerations of ICs. Each generation has smaller and more complexcircuits than the previous generation. However, these advances haveincreased the complexity of processing and manufacturing ICs.

In the course of IC evolution, functional density (i.e., the number ofinterconnected devices per chip area) has generally increased whilegeometric size (i.e., the smallest component (or line) that can becreated using a fabrication process) has decreased. This scaling-downprocess generally provides benefits by increasing production efficiencyand lowering associated costs.

However, since feature sizes (e.g., line widths) continue to decrease,fabrication processes continue to become more difficult to perform.Therefore, it is a challenge to form reliable semiconductor devices atsmaller and smaller sizes.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It shouldbe noted that, in accordance with standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A-1M are cross-sectional views of various stages of a process forforming a semiconductor device structure, in accordance with someembodiments.

FIGS. 2A-2C are cross-sectional views of various stages of a process forforming a semiconductor device structure, in accordance with someembodiments.

FIGS. 3A-3H are cross-sectional views of various stages of a process forforming a semiconductor device structure, in accordance with someembodiments.

FIGS. 4A-4F are cross-sectional views of various stages of a process forforming a semiconductor device structure, in accordance with someembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the subject matterprovided. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Furthermore, spatially relative terms, such as “beneath,” “below,”“lower,” “above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. It should be understoodthat additional operations can be provided before, during, and after themethod, and some of the operations described can be replaced oreliminated for other embodiments of the method.

FIGS. 1A-1M are cross-sectional views of various stages of a process forforming a semiconductor device structure, in accordance with someembodiments. As shown in FIG. 1A, a semiconductor substrate 110 isprovided. In some embodiments, the semiconductor substrate 110 is a bulksemiconductor substrate, such as a semiconductor wafer. For example, thesemiconductor substrate 110 is a silicon wafer.

The semiconductor substrate 110 may include silicon or anotherelementary semiconductor material such as germanium. In some otherembodiments, the semiconductor substrate 110 includes a compoundsemiconductor. The compound semiconductor may include silicon germanium,gallium arsenide, silicon carbide, indium arsenide, indium phosphide,another suitable compound semiconductor, or a combination thereof.

In some embodiments, the semiconductor substrate 110 includes asemiconductor-on-insulator (SOI) substrate. The SOI substrate may befabricated using a wafer bonding process, a silicon film transferprocess, a separation by implantation of oxygen (SIMOX) process, anotherapplicable method, or a combination thereof.

In some embodiments, various device elements are formed in and/or overthe semiconductor substrate 110. The device elements are not shown infigures for the purpose of simplicity and clarity. Examples of thevarious device elements include transistors, diodes, another suitableelement, or a combination thereof.

For example, the transistors may be metal oxide semiconductor fieldeffect transistors (MOSFET), complementary metal oxide semiconductor(CMOS) transistors, bipolar junction transistors (BJT), high-voltagetransistors, high-frequency transistors, p-channel and/or n-channelfield effect transistors (PFETs/NFETs), etc. Various processes, such asfront-end-of-line (FEOL) semiconductor fabrication processes, areperformed to form the various device elements. The FEOL semiconductorfabrication processes may include deposition, etching, implantation,photolithography, annealing, planarization, one or more other applicableprocesses, or a combination thereof.

In some embodiments, isolation features (not shown) are formed in thesemiconductor substrate 110. The isolation features are used to defineactive regions and electrically isolate various device elements formedin and/or over the semiconductor substrate 110 in the active regions. Insome embodiments, the isolation features include shallow trenchisolation (STI) features, local oxidation of silicon (LOCOS) features,other suitable isolation features, or a combination thereof.

In some embodiments, an interconnection structure (not shown) is formedover the semiconductor substrate 110 in regions 110A and 110B. Theregions 110A and 110B may be referred to as a narrow line width regionand a wide line width region, but embodiments of the disclosure are notlimited thereto.

The interconnection structure includes multiple dielectric layerscontaining an interlayer dielectric (ILD) layer and one or moreinter-metal dielectric (IMD) layers. The interconnection structure alsoincludes multiple conductive features formed in the ILD and IMD layers.The conductive features may include conductive lines, conductive vias,and/or conductive contacts. Various processes, such as back-end-of-line(BEOL) semiconductor fabrication processes, are performed to form theinterconnection structure.

Various device elements are interconnected through the interconnectionstructure over the semiconductor substrate 110 to form integratedcircuit devices. The integrated circuit devices include logic devices,memory devices (e.g., static random access memories, SRAMs), radiofrequency (RF) devices, input/output (I/O) devices, system-on-chip (SoC)devices, image sensor devices, other applicable types of devices, or acombination thereof.

As shown in FIG. 1A, a dielectric layer 120 is deposited over thesemiconductor substrate 110 in the regions 110A and 110B. The dielectriclayer 120 may serve as an ILD or IMD layer of an interconnectionstructure. The dielectric layer 120 covers device elements formed inand/or over the semiconductor substrate 110. Although FIG. 1A shows thatthe dielectric layer 120 is a single layer, embodiments of thedisclosure are not limited thereto. In some other embodiments, thedielectric layer 120 is a multi-layer structure including dielectricsub-layers (not shown).

In some embodiments, the dielectric layer 120 is made of or includes aninsulating material, such as silicon oxide, silicon oxynitride, a lowdielectric constant (low-k) material, an extreme low-k (ELK) material,borosilicate glass (BSG), phosphoric silicate glass (PSG),borophosphosilicate glass (BPSG), fluorinated silicate glass (FSG), oneor more other suitable materials, or a combination thereof. In someembodiments, the dielectric layer 120 is deposited using a chemicalvapor deposition (CVD) process, an atomic layer deposition (ALD)process, a spin-on process, a spray coating process, one or more otherapplicable processes, or a combination thereof.

The low-k or ELK material may have a smaller dielectric constant thanthat of silicon dioxide. For example, the low-k material may have adielectric constant in a range from about 1.5 to about 3.5. The ELKmaterial may have a dielectric constant, which is less than about 2.5 orin a range from about 1.5 to about 2.5. As the density of semiconductordevices increases and the size of circuit elements becomes smaller, theresistance capacitance (RC) delay time increasingly dominates circuitperformance. Therefore, using a low-k or ELK material as the dielectriclayer 120 is helpful in reducing the RC delay.

A wide variety of low-k or ELK material may be used for forming thedielectric layer 120. In some embodiments, the dielectric layer 120 ismade of or includes a porous dielectric material, an organic polymer, anorganic silica glass, SiOF series material, a hydrogen silsesquioxane(HSQ) series material, a methyl silsesquioxane (MSQ) series material,carbon doped silicon oxide, amorphous fluorinated carbon, parylene,benzocyclobutenes (BCB), polytetrafluoroethylene (PTFE) (Teflon),silicon oxycarbide polymers (SiOC), a porous organic series material, aspin-on inorganic dielectric, a spin-on organic dielectric material, oneor more other suitable materials, or a combination thereof.

Multiple conductive features (not shown) are formed in the dielectriclayer 120 in the regions 110A and 110B. The conductive features may beelectrically connected to gate structures or power devices formed on thesemiconductor substrate 110 or doped regions formed in the semiconductorsubstrate 110. The conductive features in the region 110A may beelectrically connected to the gate structures and the doped regions, andthe conductive features in the region 110B may be electrically connectedto the power devices.

The conductive features may include conductive lines, conductive vias,conductive contacts, or a combination thereof. In some embodiments, theconductive features are made of or include a conductive material, suchas a metal material (e.g., copper, aluminum, tungsten, titanium, cobalt,nickel, gold, platinum, or a combination thereof). Various processes,including deposition, etching, planarization, or the like, may be usedto form the conductive features in the dielectric layer 120.

As shown in FIG. 1A, a mask layer 130 is deposited over the dielectriclayer 120, in accordance with some embodiments. The mask layer 130 isalso referred to as an anti-reflective coating (ARC) layer, inaccordance with some embodiments. The mask layer 130 may absorb lightthereby minimizing reflection during a subsequent photolithographyprocess so as to enhance the resolution of the photolithography process.In some embodiments, the mask layer 130 is made of or includes ananti-reflective material, such as SiON, SiCN, SiN, HfO, Al₂O₃, Ta₂O₅,ZrO, one or more other suitable materials, or a combination thereof.

In some embodiments, the mask layer 130 is a nitrogen-freeanti-reflective coating (NFARC) layer. By keeping an interface betweenthe dielectric layer 120 and the mask layer 130 nitrogen free, little orno nitrogen diffuses into the dielectric layer 120 so as to preventcontamination. The mask layer 130 is deposited using a spray coatingprocess, a spin-on process, a CVD process, an ALD process, one or moreother applicable processes, or a combination thereof.

As shown in FIG. 1A, a hard mask layer 140 is deposited over the masklayer 130. The hard mask layer 140 is made of or includes titaniumnitride (TiN), SiON, one or more other suitable materials, or acombination thereof. In some other embodiments, the hard mask layer 140is a multi-layer structure, such as oxide-nitride-oxide (ONO) layers.The hard mask layer 140 is deposited using a PVD process (such as aradio-frequency PVD (RFPVD) process), a CVD process, an ALD process, oneor more other applicable processes, or a combination thereof.

As shown in FIG. 1A, a mask layer 150 is deposited over the hard masklayer 140, in accordance with some embodiments. The mask layer 150 isalso referred to as an anti-reflective coating (ARC) layer, inaccordance with some embodiments. The mask layer 150 is made of orincludes an anti-reflective material, such as SiON, SiCN, SiN, HfO,Al₂O₃, Ta₂O₅, ZrO, one or more other suitable materials, or acombination thereof.

In some embodiments, the mask layer 150 and the mask layer 130 are madeof or include the same material. In some embodiments, the dielectriclayer 120 and the mask layer 150 are made of different materials. Insome embodiments, the hard mask layer 140 and the mask layer 150 aremade of different materials.

In some embodiments, the mask layer 150 is a nitrogen-freeanti-reflective coating (NFARC) layer. The mask layer 150 is depositedusing a spray coating process, a spin-on process, a CVD process, an ALDprocess, one or more other applicable processes, or a combinationthereof.

Afterwards, as shown in FIG. 1B, a patterned mask structure M1 is formedover the mask layer 150, in accordance with some embodiments. Thepatterned mask structure M1 is a multi-layer mask structure, inaccordance with some embodiments. The patterned mask structure M1includes a lower layer 160, a middle layer 170 and an upper layer 180,in accordance with some embodiments.

As shown in FIG. 1B, the lower layer 160, the middle layer 170 and theupper layer 180 are sequentially deposited over the mask layer 150, inaccordance with some embodiments. In some embodiments, the lower layer160 is made of or includes a polymer material. In some embodiments, themiddle layer 170 is made of or includes a silicon-containing material,such as a silicon-containing polymer material. In some embodiments, theupper layer 180 is made of or includes a photoresist material. In someembodiments, the lower layer 160, the middle layer 170 and the upperlayer 180 are deposited using a PVD process, a CVD process, a spin-onprocess, another applicable process, or a combination thereof.

The upper layer 180 is patterned to form trenches 182 in the upper layer180, in accordance with some embodiments. The trenches 182 partiallyexpose the middle layer 170. The upper layer 180 is patterned by aphotolithography process. Afterwards, the middle layer 170 is patternedor etched using the patterned upper layer 180 as an etch mask. As aresult, the trenches 182 are transferred into the middle layer 170 (notshown).

The patterned upper layer 180 may be removed during the patterning ofthe middle layer 170. Similarly, the lower layer 160 is then patternedor etched using the patterned middle layer 170 as an etch mask. As aresult, the trenches 182 are transferred into the lower layer 160 (notshown). The patterned middle layer 170 may be removed during thepatterning of the lower layer 160.

The patterned lower layer 160 is subsequently used as an etch mask topattern the mask layer 150. As shown in FIG. 1C, the mask layer 150 ispatterned or etched using the patterned lower layer 160 as an etch mask,in accordance with some embodiments. As a result, trenches 151 and 153are formed in the mask layer 150, in accordance with some embodiments.The trenches 151 and 153 penetrate through the mask layer 150, inaccordance with some embodiments. The trenches 151 and 153 partiallyexpose the hard mask layer 140 thereunder, in accordance with someembodiments. The patterned lower layer 160 may be removed during thepatterning of the mask layer 150.

In some embodiments, the middle layer 170, the lower layer 160, and themask layer 150 are sequentially patterned using one or more etchingprocesses. The etching process may be a dry etching process, one or moreother applicable processes, or a combination thereof.

Afterwards, as shown in FIG. 1D, a patterned mask structure M2 is formedover the mask layer 150, in accordance with some embodiments. Thepatterned mask structure M2 is a multi-layer mask structure, inaccordance with some embodiments. The patterned mask structure M2includes a lower layer 190, a middle layer 200, and an upper layer 210,in accordance with some embodiments.

As shown in FIG. 1D, the lower layer 190, the middle layer 200, and theupper layer 210 are sequentially deposited over the mask layer 150, inaccordance with some embodiments. In some embodiments, the lower layer190 is made of or includes a polymer material. In some embodiments, themiddle layer 200 is made of or includes a silicon-containing material,such as a silicon-containing polymer material. In some embodiments, theupper layer 210 is made of or includes a photoresist material. In someembodiments, the lower layer 190, the middle layer 200 and the upperlayer 210 are deposited using a PVD process, a CVD process, a spin-onprocess, another applicable process, or a combination thereof.

The upper layer 210 is patterned to form trenches 212 in the upper layer210, in accordance with some embodiments. The trenches 212 partiallyexpose the middle layer 200. The upper layer 210 is patterned by aphotolithography process.

Afterwards, the middle layer 200 is patterned or etched using thepatterned upper layer 210 as an etch mask. As a result, the trenches 212are transferred into the middle layer 200 (not shown). The patternedupper layer 210 may be removed during the patterning of the middle layer200. Similarly, the lower layer 190 is then patterned or etched usingthe patterned middle layer 200 as an etch mask. As a result, thetrenches 212 are transferred into the lower layer 190 (not shown). Thepatterned middle layer 200 may be removed during the patterning of thelower layer 190.

The patterned lower layer 190 is subsequently used as an etch mask topattern the mask layer 150. As shown in FIG. 1E, the mask layer 150 ispatterned and etched using the patterned lower layer 190 as an etchmask. As a result, trenches 152 and 154 are formed in the mask layer150. The trenches 152 and 154 penetrate through the mask layer 150. Thetrenches 152 and 154 partially expose the hard mask layer 140thereunder, in accordance with some embodiments. The patterned lowerlayer 190 may be removed during the patterning of the mask layer 150.

In some embodiments, the middle layer 200, the lower layer 190 and themask layer 150 are sequentially patterned using one or more etchingprocesses. The etching process may be a dry etching process, one or moreother applicable processes, or a combination thereof.

Afterwards, as shown in FIG. 1E, the trenches 151, 152, 153, and 154respectively have widths W1, W2, W3 and W4, in accordance with someembodiments. The widths W1, W2, W3 and W4 are substantially equal toeach other, in accordance with some embodiments. The term “substantiallyequal to” means “within 10%”, in accordance with some embodiments.

For example, the term “substantially equal to” means the differencebetween the widths W1, W2, W3 and W4 is within 10% of the average widthof the trenches 151, 152, 153, and 154, in accordance with someembodiments. The trenches 151, 152, 153, and 154 have inner walls N1,N2, N3, and N4 and bottom surfaces B1, B2, B3 and B4, in accordance withsome embodiments.

Thereafter, as shown in FIG. 1F, a mask layer 220 is deposited over themask layer 150 and in the trenches 151, 152, 153, and 154, in accordancewith some embodiments. The mask layer 220 conformally covers a topsurface 155 of the mask layer 150, the inner walls N1, N2, N3, and N4,and the bottom surfaces B1, B2, B3 and B4, in accordance with someembodiments. The mask layer 220 is in direct contact with the masklayers 140 and 150, in accordance with some embodiments.

In some embodiments, a first thickness T1 of the mask layer 220 over thetop surface 155 is greater than a second thickness T2 of the mask layer220 over the inner walls N1, N2, N3, and N4. The second thickness T2 isgreater than a third thickness T3 of the mask layer 220 over the bottomsurfaces B1, B2, B3 and B4, in accordance with some embodiments.

The mask layer 220 is also referred to as an anti-reflective coating(ARC) layer, in accordance with some embodiments. The mask layer 220 ismade of or includes an anti-reflective material, such as SiON, SiCN,SiN, HfO, Al₂O₃, Ta₂O₅, ZrO, one or more other suitable materials, or acombination thereof.

In some embodiments, the mask layer 220 and the mask layer 150 are madeof or include the same material. In some embodiments, the mask layer 220is a nitrogen-free anti-reflective coating (NFARC) layer. The mask layer220 is deposited using a CVD process, an ALD process, one or more otherapplicable processes, or a combination thereof.

As shown in FIG. 1G, the mask layer 220 covering the bottom surfaces B1,B2, B3, and B4 is removed to form trenches 222, 224, 226, and 228 in themask layer 220, in accordance with some embodiments. The trenches 222,224, 226, and 228 respectively expose the bottom surfaces B1, B2, B3,and B4, in accordance with some embodiments.

The trenches 222 and 224 respectively have widths W5 and W6, inaccordance with some embodiments. The width W5 or W6 is less than thewidth W1, W2, W3, or W4, in accordance with some embodiments. After theremoval process, the remaining mask layer 220 covers the inner walls N1,N2, N3, and N4 and the top surface 155, in accordance with someembodiments. The removal process includes a dry etching process (e.g.,an anisotropic etching process) or a wet etching process, in accordancewith some embodiments. The dry etching process includes a plasma etchingprocess, in accordance with some embodiments.

As shown in FIG. 1H, a photoresist layer 230 is formed over the masklayer 220 in the region 110A, in accordance with some embodiments. Thephotoresist layer 230 is filled in the trenches 151 and 152, inaccordance with some embodiments. As shown in FIG. 11, the mask layer220 in the region 110B is removed, in accordance with some embodiments.The removal process includes an etching process, such as a dry etchingprocess, in accordance with some embodiments.

As shown in FIG. 1J, the photoresist layer 230 is removed, in accordancewith some embodiments. The mask layer 220 has a sidewall 229 alignedwith the boundary between the regions 110A and 110B, in accordance withsome embodiments. In some embodiments, a ratio of the thickness T2 ofthe mask layer 220 over the inner wall N1 to the width W1 of the trench151 ranges from about 0.16 to about 0.4. In some embodiments, a ratio ofthe width W5 of the trench 222 to the width W1 of the trench 151 rangesfrom about 0.16 to about 0.66. In some embodiments, a distance D1between the trenches 222 and 224 is less than a distance D2 between thetrenches 153 and 154.

The mask layers 150 and 220 are used as an etch mask in subsequentprocesses for forming conductive lines, in accordance with someembodiments. Although the widths W1, W2, W3, and W4 of the trenches 151,152, 153, and 154 are substantially equal to each other, the mask layer220 formed over the inner walls N1 and N2 of the trenches 151 and 152has the trenches 222 and 224 that are narrower than the trenches 151,152, 153, and 154. Therefore, the formation of the mask layer 220 maynarrow the subsequently formed conductive lines by using the mask layer220 as an etch mask.

As shown in FIG. 1K, portions of the hard mask layer 140, the mask layer130, and the dielectric layer 120 under the trenches 222, 224, 153, and154 are removed to form trenches R1, R2, R3, and R4 in the hard masklayer 140, the mask layer 130, and the dielectric layer 120, inaccordance with some embodiments.

The trenches R1, R2, R3, and R4 pass through the hard mask layer 140 andthe mask layer 130 and penetrate into the dielectric layer 120, inaccordance with some embodiments. The trenches R1, R2, R3, and R4respectively have widths W7, W8, W9, and W10, in accordance with someembodiments. The width W7 or W8 is less than the width W9 or W10, inaccordance with some embodiments.

The removal process includes an etching process using the mask layers150 and 220 as an etch mask, in accordance with some embodiments. Themask layers 150 and 220 may be consumed during the removal process. Insome embodiments, an upper portion of the hard mask layer 140 isconsumed during the removal process.

Since the mask layer 220 covers the hard mask layer 140 in the region110A during the removal process, the hard mask layer 140 remaining inthe region 110A is thicker than the hard mask layer 140 remaining in theregion 110B. That is, a thickness T9 of the hard mask layer 140 in theregion 110A is greater than a thickness T10 of the hard mask layer 140in the region 110B, in accordance with some embodiments. In someembodiments, the hard mask layer 140 remaining in the region 110A isalso referred to as a thick portion, and the hard mask layer 140remaining in the region 110B is also referred to as a thin portion. Insome embodiments, the boundary between the thick portion and the thinportion is substantially aligned with the sidewall 229 of the mask layer220 (as shown in FIG. 1J).

As shown in FIG. 1L, a barrier layer 240 is deposited over the hard masklayer 140, the mask layer 130, and the dielectric layer 120, inaccordance with some embodiments. The barrier layer 240 may preventmetal ions of a subsequently deposited conductive material (which willbe described in more detail later) from diffusing into the dielectriclayer 120 during thermal processes or cycles. The barrier layer 240 mayalso be referred to as a diffusion barrier layer.

In some embodiments, the barrier layer 240 is made of or includes arefractory metal material, such as tantalum (Ta), titanium (Ti),tantalum nitride, titanium nitride, one or more other suitablematerials, or a combination thereof. In some embodiments, the barrierlayer 240 is deposited using a PVD process, an ALD process, one or moreother applicable processes, or a combination thereof. In someembodiments, the barrier layer 240 is deposited conformally.

As shown in FIG. 1L, a conductive material layer 250 is formed over thebarrier layer 240, in accordance with some embodiments. The trenches R1,R2, R3, and R4 are filled with the conductive material layer 250 and thebarrier layer 240, in accordance with some embodiments. In someembodiments, the conductive material layer 250 is made of or includes ametal material, such as copper, aluminum, tungsten, titanium, nickel,gold, platinum, silver, one or more other suitable materials, or acombination thereof.

The conductive material layer 250 may be a single layer or have multiplestacked layers. The conductive material layer 250 is deposited using anelectroplating process, a PVD process, a CVD process, an electrolessplating process, another applicable process, or a combination thereof.

As shown in FIG. 1M, the conductive material layer 250 and the barrierlayer 240 outside of the trenches R1, R2, R3, and R4, the hard masklayer 140, and the mask layer 130 are removed, in accordance with someembodiments. The conductive material layer 250 and the barrier layer 240remaining in the trenches R1, R2, R3, and R4 forms conductive structuresL1, L2, L3, and L4 respectively in the trenches R1, R2, R3, and R4, inaccordance with some embodiments.

The conductive structures L1, L2, L3, and L4 include conductive lines,in accordance with some embodiments. The conductive structures L1, L2,L3, and L4 respectively have widths (or line widths) W11, W12, W13, andW14, in accordance with some embodiments. Since the width W7 or W8 isless than the width W9 or W10 (as shown in FIG. 1K), the width W11 orW12 is less than the width W13 or W14. The widths W11 and W12 aresubstantially equal to each other, in accordance with some embodiments.The widths W13 and W14 are substantially equal to each other, inaccordance with some embodiments.

The conductive structures L1 and L2 are positioned in the region 110A,and the conductive structures L3 and L4 are positioned in the region110B, in accordance with some embodiments. The distance D1 between theconductive structures L1 and L2 is less than the distance D2 between theconductive structures L3 and L4, in accordance with some embodiments.

The regions 110A and 110B may be respectively referred to as a smallpitch region and a large pitch region. A pitch of a region is equal to asum of a width of one of conductive structures and a spacing between twoadjacent conductive structures in the region. The pitch of the region110A is equal to a sum of the width W11 (or W12) and the distance D1, inaccordance with some embodiments. The pitch of the region 110B is equalto a sum of the width W13 (or W14) and the distance D2, in accordancewith some embodiments. Since the width W11 (or W12) is less than the W13(or W14) and the distance D1 is less than the distance D2, the pitch ofthe region 110A is less than the pitch of the region 110B.

The removal process includes a planarization process, in accordance withsome embodiments. Therefore, top surfaces S1, S2, S3, S4, and 122 of theconductive structures L1, L2, L3, and L4 and the dielectric layer 120are coplanar, in accordance with some embodiments.

FIGS. 2A-2C are cross-sectional views of various stages of a process forforming a semiconductor device structure, in accordance with someembodiments. The embodiment of FIGS. 2A-2C is similar to the embodimentof FIGS. 1A-1M, except that the embodiment of FIGS. 2A-2C removes themask layer 220 in the region 110B firstly (as shown in FIG. 2B) and thenremoves the mask layer 220 covers the bottom surfaces B1 and B2 (asshown in FIG. 2C), in accordance with some embodiments.

After the step of FIG. 1F, as shown in FIG. 2A, a photoresist layer 230is formed over the mask layer 220 in the region 110A, in accordance withsome embodiments. Afterwards, as shown in FIG. 2B, the mask layer 220 inthe region 110B is removed, in accordance with some embodiments. Theremoval process includes an etching process using the photoresist layer230 as an etch mask, in accordance with some embodiments.

As shown in FIG. 2C, the photoresist layer 230 is removed, in accordancewith some embodiments. As shown in FIG. 2C, the mask layer 220 coveringthe bottom surfaces B1 and B2 is removed to form trenches 222 and 224 inthe mask layer 220, in accordance with some embodiments. The trenches222 and 224 respectively expose the bottom surfaces B1 and B2, inaccordance with some embodiments. Afterwards, the steps of FIGS. 1K-1Mare performed to form the conductive structures L1, L2, L3, and L4 (asshown in FIG. 1M), in accordance with some embodiments.

FIGS. 3A-3H are cross-sectional views of various stages of a process forforming a semiconductor device structure, in accordance with someembodiments. After the step of FIG. 1E, as shown in FIG. 3A, a masklayer 310 is formed over the top surface 155 of the mask layer 150 andthe inner walls N1, N2, N3, and N4 of the trenches 151, 152, 153, and154, in accordance with some embodiments.

In some embodiments, a thickness T4 of the mask layer 310 over the innerwalls N1, N2, N3, and N4 increases in a direction V1 away from thedielectric layer 120. The mask layer 310 has trenches 312, 314, 316, and318 respectively in the trenches 151, 152, 153, and 154, in accordancewith some embodiments. The trenches 312, 314, 316, and 318 respectivelyexpose the bottom surfaces B1, B2, B3, and B4 of the trenches 151, 152,153, and 154, in accordance with some embodiments.

The mask layer 310 covering the top surface 155 is thicker than the masklayer 310 covering the inner walls N1, N2, N3, and N4 of the trenches151, 152, 153, and 154, in accordance with some embodiments. That is, amaximum thickness T5 of the mask layer 310 covering the top surface 155is greater than a maximum thickness T4′ of the mask layer 310 over theinner walls N1, N2, N3, and N4, in accordance with some embodiments.

The mask layer 310 is also referred to as an anti-bombardment layer, inaccordance with some embodiments. The mask layer 310 is used to maintainthe height of the mask layer 150 thereunder for a longer time duringsubsequent etching processes (e.g. dry etching processes) for formingtrenches in the dielectric layer 120, in accordance with someembodiments.

The mask layer 310 is made of an anti-bombardment material, such as anitride material (e.g., titanium nitride or tantalum nitride), inaccordance with some embodiments. The mask layer 310 is formed using aCVD process or an ALD process, in accordance with some embodiments. Themask layer 310 is deposited at a first deposition pressure, inaccordance with some embodiments. The mask layer 310 is deposited with afirst deposition power, in accordance with some embodiments.

As shown in FIG. 3B, a mask layer 220 is formed over the mask layer 310and the hard mask layer 140 exposed by the trenches 151, 152, 153, and154, in accordance with some embodiments. The mask layer 220 covers theinner walls N1, N2, N3, and N4 and the bottom surfaces B1, B2, B3 and B4of the trenches 151, 152, 153, and 154, in accordance with someembodiments.

The mask layer 220 is also referred to as an anti-chemical etchingprotective layer, in accordance with some embodiments. The mask layer220 is used to protect the inner walls N1, N2, N3, and N4 duringsubsequent etching processes (e.g. dry etching processes) for formingtrenches in the dielectric layer 120, in accordance with someembodiments. The mask layer 220 is in direct contact with the masklayers 150 and 310 and the hard mask layer 140, in accordance with someembodiments.

In some embodiments, a first thickness T6 of the mask layer 220 over thetop surface 155 is greater than a second thickness T7 of the mask layer220 over the inner walls N1, N2, N3, and N4. The second thickness T7 isgreater than a third thickness T8 of the mask layer 220 over the bottomsurfaces B1, B2, B3 and B4, in accordance with some embodiments.

The mask layers 220 and 310 are made of different materials, inaccordance with some embodiments. The mask layer 220 is made of orincludes an anti-chemical etching material, such as a nitride material(e.g, SiON, SiCN, SiN) or a low temperature oxide material (e.g.,silicon dioxide), in accordance with some embodiments. The mask layer220 is deposited using a CVD process, an ALD process, one or more otherapplicable processes, or a combination thereof.

The mask layer 220 is deposited at a second deposition pressure, inaccordance with some embodiments. The mask layer 220 is deposited with asecond deposition power, in accordance with some embodiments. If thedeposition pressure is high and the deposition power is low, thedeposited layer tends to be deposited outside of the trenches. If thedeposition pressure is low and the deposition power is large, thedeposited layer tends to be deposited in the trenches. Therefore, thefirst deposition pressure is greater than the second depositionpressure, in accordance with some embodiments. The first depositionpower is less than the second deposition power, in accordance with someembodiments.

As shown in FIG. 3C, the mask layer 220 over the bottom surfaces B1, B2,B3 and B4 is removed, in accordance with some embodiments. The removalprocess forms trenches 222, 224, 226, and 228 in the mask layer 220, inaccordance with some embodiments. The trenches 222, 224, 226, and 228are respectively positioned in the trenches 312, 314, 316, and 318, inaccordance with some embodiments. The trenches 222, 224, 226, and 228respectively expose the bottom surfaces B1, B2, B3 and B4, in accordancewith some embodiments. The removal process includes an etching process,such a dry etching process or a wet etching process, in accordance withsome embodiments.

As shown in FIG. 3D, a photoresist layer 230 is formed over the masklayer 220 in the region 110A, in accordance with some embodiments. Thephotoresist layer 230 is filled in the trenches 151 and 152, inaccordance with some embodiments. As shown in FIG. 3E, the mask layers220 and 310 in the region 110B are removed, in accordance with someembodiments. The removal process includes an etching process, such as adry etching process, in accordance with some embodiments.

As shown in FIG. 3F, the photoresist layer 230 is removed, in accordancewith some embodiments. In some embodiments, a distance D1 between thetrenches 222 and 224 is less than a distance D2 between the trenches 153and 154. The mask layers 150, 220, and 310 are used as an etch mask insubsequent processes for forming conductive lines, in accordance withsome embodiments.

As shown in FIG. 3G, portions of the hard mask layer 140, the mask layer130, and the dielectric layer 120 under the trenches 222, 224, 153, and154 are removed to form trenches R1, R2, R3, and R4 in the hard masklayer 140, the mask layer 130, and the dielectric layer 120, inaccordance with some embodiments.

The trenches R1, R2, R3, and R4 pass through the hard mask layer 140 andthe mask layer 130 and penetrate into the dielectric layer 120, inaccordance with some embodiments. The trenches R1, R2, R3, and R4respectively have widths W7, W8, W9, and W10, in accordance with someembodiments. The width W7 or W8 is less than the width W9 or W10, inaccordance with some embodiments.

The removal process includes an etching process using the mask layers150, 220, and 310 as an etch mask, in accordance with some embodiments.The mask layers 150, 220, and 310 may be consumed during the removalprocess. In some embodiments, an upper portion of the hard mask layer140 is consumed during the removal process.

Since the mask layer (or the anti-bombardment layer) 310 covers the topsurface 155 of the mask layer 150, the height of the mask layer 150 ismaintained for a longer time during the removal process, as shown inFIGS. 3F and 3G, in accordance with some embodiments. Since the masklayer 220 is made of an anti-chemical etching material, the widths W5and W6 of the trenches 222 and 224 of the mask layer 220 are maintainedfor a longer time during the removal process, as shown in FIGS. 3F and3G, in accordance with some embodiments. Therefore, the formation of themask layers 220 and 310 may improve the yield of the trenches R1 and R2,as shown in FIGS. 3F and 3G.

As shown in FIG. 3G, a barrier layer 240 is deposited over the hard masklayer 140, the mask layer 130, and the dielectric layer 120, inaccordance with some embodiments. The barrier layer 240 may preventmetal ions of a subsequently deposited conductive material (which willbe described in more detail later) from diffusing into the dielectriclayer 120 during thermal processes or cycles. The barrier layer 240 mayalso be referred to as a diffusion barrier layer.

In some embodiments, the barrier layer 240 is made of or includes arefractory metal material, such as tantalum (Ta), titanium (Ti),tantalum nitride, titanium nitride, one or more other suitablematerials, or a combination thereof. In some embodiments, the barrierlayer 240 is deposited using a PVD process, an ALD process, one or moreother applicable processes, or a combination thereof. In someembodiments, the barrier layer 240 is deposited conformally.

As shown in FIG. 3G, a conductive material layer 250 is formed over thebarrier layer 240, in accordance with some embodiments. The trenches R1,R2, R3, and R4 are filled with the conductive material layer 250 and thebarrier layer 240, in accordance with some embodiments.

As shown in FIG. 3H, the conductive material layer 250 and the barrierlayer 240 outside of the trenches R1, R2, R3, and R4, the hard masklayer 140, and the mask layer 130 are removed, in accordance with someembodiments. The conductive material layer 250 and the barrier layer 240remaining in the trenches R1, R2, R3, and R4 forms conductive structuresL1, L2, L3, and L4 respectively in the trenches R1, R2, R3, and R4, inaccordance with some embodiments.

The conductive structures L1, L2, L3, and L4 include conductive lines,in accordance with some embodiments. The conductive structures L1, L2,L3, and L4 respectively have widths (or line widths) W11, W12, W13, andW14, in accordance with some embodiments. Since the width W7 or W8 isless than the width W9 or W10 (as shown in FIG. 3G), the width W11 orW12 is less than the width W13 or W14.

The conductive structures L1 and L2 are positioned in the region 110A,and the conductive structures L3 and L4 are positioned in the region110B, in accordance with some embodiments. The distance D1 between theconductive structures L1 and L2 is less than the distance D2 between theconductive structures L3 and L4, in accordance with some embodiments.

The removal process includes a planarization process, in accordance withsome embodiments. Therefore, top surfaces S1, S2, S3, S4, and 122 of theconductive structures L1, L2, L3, and L4 and the dielectric layer 120are coplanar, in accordance with some embodiments.

FIGS. 4A-4F are cross-sectional views of various stages of a process forforming a semiconductor device structure, in accordance with someembodiments. After the step of FIG. 1E, as shown in FIG. 4A, a masklayer 220 is conformally formed over the top surface 155 of the masklayer 150, the inner walls N1, N2, N3, and N4, and the bottom surfacesB1, B2, B3, and B4 of the trenches 151, 152, 153, and 154, in accordancewith some embodiments. The mask layer 220 is made of or includes ananti-chemical etching material, such as a nitride material (e.g, SiON,SiCN, or SiN) or a low temperature oxide material (e.g., silicondioxide), in accordance with some embodiments.

As shown in FIG. 4B, the mask layer 220 over the bottom surfaces B1, B2,B3, and B4 is removed, in accordance with some embodiments. The masklayer 220 has trenches 222, 224, 226, and 228, in accordance with someembodiments. As shown in FIG. 4C, a mask layer 310 is formed over themask layer 220, in accordance with some embodiments.

The mask layer 310 covers a top surface 221 of the mask layer 220 andinner walls 222 a, 224 a, 226 a, and 228 a of the trenches 222, 224,226, and 228, in accordance with some embodiments. In some embodiments,a thickness T4 of the mask layer 310 over the inner walls 222 a, 224 a,226 a, and 228 a increases in a direction V1 away from the dielectriclayer 120. The mask layer 310 is made of an anti-bombardment material,such as a nitride material (e.g., titanium nitride or tantalum nitride),in accordance with some embodiments. The mask layers 220 and 310 aremade of different materials, in accordance with some embodiments.

As shown in FIG. 4D, the mask layers 220 and 310 in the region 110B areremoved, in accordance with some embodiments. As shown in FIG. 4E,portions of the hard mask layer 140, the mask layer 130, and thedielectric layer 120 under the trenches 222, 224, 153, and 154 areremoved to form trenches R1, R2, R3, and R4 in the hard mask layer 140,the mask layer 130, and the dielectric layer 120, in accordance withsome embodiments.

The trenches R1, R2, R3, and R4 pass through the hard mask layer 140 andthe mask layer 130 and penetrate into the dielectric layer 120, inaccordance with some embodiments. The removal process includes anetching process using the mask layers 150, 220, and 310 as an etch mask,in accordance with some embodiments. The mask layers 150, 220, and 310may be consumed during the removal process. In some embodiments, anupper portion of the hard mask layer 140 is consumed during the removalprocess.

Since the mask layer (or the anti-bombardment layer) 310 covers the topsurface 155 of the mask layer 150, the height of the mask layer 150 ismaintained for a longer time during the removal process, as shown inFIGS. 4D and 4E, in accordance with some embodiments. Since the masklayer 220 is made of an anti-chemical etching material, the widths W5and W6 of the trenches 222 and 224 of the mask layer 220 are maintainedfor a longer time during the removal process, as shown in FIGS. 4D and4E, in accordance with some embodiments. Therefore, the formation of themask layers 220 and 310 may improve the yield of the trenches R1 and R2,as shown in FIGS. 4D and 4E.

As shown in FIG. 4E, a barrier layer 240 is deposited over the hard masklayer 140, the mask layer 130, and the dielectric layer 120, inaccordance with some embodiments. As shown in FIG. 4E, a conductivematerial layer 250 is formed over the barrier layer 240, in accordancewith some embodiments.

As shown in FIG. 4F, the conductive material layer 250 and the barrierlayer 240 outside of the trenches R1, R2, R3, and R4, the hard masklayer 140, and the mask layer 130 are removed, in accordance with someembodiments. The conductive material layer 250 and the barrier layer 240remaining in the trenches R1, R2, R3, and R4 forms conductive structuresL1, L2, L3, and L4 respectively in the trenches R1, R2, R3, and R4, inaccordance with some embodiments.

The conductive structures L1, L2, L3, and L4 include conductive lines,in accordance with some embodiments. The conductive structures L1, L2,L3, and L4 respectively have widths (or line widths) W11, W12, W13, andW14, in accordance with some embodiments. The width W11 or W12 is lessthan the width W13 or W14, in accordance with some embodiments. Thedistance D1 between the conductive structures L1 and L2 is less than thedistance D2 between the conductive structures L3 and L4, in accordancewith some embodiments.

The removal process includes a planarization process, in accordance withsome embodiments. Therefore, top surfaces S1, S2, S3, S4, and 122 of theconductive structures L1, L2, L3, and L4 and the dielectric layer 120are coplanar, in accordance with some embodiments.

In accordance with some embodiments, methods for forming semiconductordevice structures are provided. The methods (for forming thesemiconductor device structure) include: forming a first mask layer overa dielectric layer; conformally forming a second mask layer over aninner wall of a first trench of the first mask layer; and removing thedielectric layer through the first trench to form a second trench in thedielectric layer. The formation of the second mask layer over the innerwall is able to narrow the second trench.

In accordance with some embodiments, a method for forming asemiconductor device structure is provided. The method includes forminga first mask layer over a dielectric layer. The first mask layer has afirst trench, and the first trench has an inner wall and a bottomsurface. The method includes forming a second mask layer over a firsttop surface of the first mask layer, the inner wall, and the bottomsurface. The method includes removing the second mask layer covering thebottom surface to form a second trench in the second mask layer. Thesecond trench exposes the bottom surface and is over a first portion ofthe dielectric layer. The method includes forming an anti-bombardmentlayer over a second top surface of the second mask layer. The secondmask layer and the anti-bombardment layer are made of differentmaterials. The method includes removing the first portion, the firstmask layer, the second mask layer, and the anti-bombardment layer toform a third trench in the dielectric layer. The method includes forminga conductive structure in the third trench.

In accordance with some embodiments, a method for forming asemiconductor device structure is provided. The method includes forminga first mask layer over a dielectric layer. The first mask layer has afirst trench and a second trench, and the first trench has a first innerwall and a first bottom surface. The method includes forming a secondmask layer over the first inner wall. The second mask layer has a thirdtrench in the first trench and exposing the first bottom surface, thethird trench is narrower than the second trench, and the third trenchand the second trench are respectively over a first portion and a secondportion of the dielectric layer. The method includes. The methodincludes forming an anti-bombardment layer over a first top surface ofthe first mask layer and a second top surface of the second mask layer.The second mask layer and the anti-bombardment layer are made ofdifferent materials. The method includes removing the first portion, thesecond portion, the first mask layer, the second mask layer, and theanti-bombardment layer to form a fourth trench and a fifth trench in thedielectric layer. The fourth trench is narrower than the fifth trench.The method includes forming a first conductive structure and a secondconductive structure respectively in the fourth trench and the fifthtrench.

In accordance with some embodiments, a method for forming asemiconductor device structure is provided. The method includes forminga first mask layer over a dielectric layer. The first mask layer has afirst trench and a second trench, and the first trench has an inner walland a bottom surface. The method includes forming a second mask layerover a first portion of a top surface of the first mask layer and theinner wall. The second mask layer exposes a second portion of the topsurface, the first portion and the second portion are respectivelyadjacent to the first trench and the second trench, the second masklayer has a third trench in the first trench and exposing the bottomsurface, and the third trench and the second trench are respectivelyover a third portion and a fourth portion of the dielectric layer. Themethod includes removing the third portion, the fourth portion, thefirst mask layer, and the second mask layer to form a fourth trench anda fifth trench in the dielectric layer. The fourth trench is narrowerthan the fifth trench. The method includes forming a first conductivestructure and a second conductive structure respectively in the fourthtrench and the fifth trench.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for forming a semiconductor devicestructure, comprising: forming a first mask layer over a dielectriclayer, wherein the first mask layer has a first trench, and the firsttrench has an inner wall and a bottom surface; forming a second masklayer over a first top surface of the first mask layer, the inner wall,and the bottom surface; removing the second mask layer covering thebottom surface to form a second trench in the second mask layer, whereinthe second trench exposes the bottom surface and is over a first portionof the dielectric layer; forming an anti-bombardment layer over a secondtop surface of the second mask layer, wherein the second mask layer andthe anti-bombardment layer are made of different materials; removing thefirst portion, the first mask layer, the second mask layer, and theanti-bombardment layer to form a third trench in the dielectric layer;and forming a conductive structure in the third trench.
 2. The methodfor forming the semiconductor device structure as claimed in claim 1,wherein the anti-bombardment layer covers a sidewall of the second masklayer.
 3. The method for forming the semiconductor device structure asclaimed in claim 2, wherein the anti-bombardment layer covers an upperportion of the sidewall and exposes a lower portion of the sidewall. 4.The method for forming the semiconductor device structure as claimed inclaim 2, wherein the anti-bombardment layer and the first mask layer aremade of different materials.
 5. The method for forming the semiconductordevice structure as claimed in claim 2, wherein the anti-bombardmentlayer over the second top surface of the second mask layer is thickerthan the anti-bombardment layer over the sidewall of the second masklayer.
 6. The method for forming the semiconductor device structure asclaimed in claim 1, wherein the anti-bombardment layer has a fourthtrench exposing the bottom surface and is over the first portion of thedielectric layer.
 7. The method for forming the semiconductor devicestructure as claimed in claim 6, wherein the removing of the firstportion of the dielectric layer comprises: removing the first portionthrough the second trench of the second mask layer and the fourth trenchof the anti-bombardment layer.
 8. The method for forming thesemiconductor device structure as claimed in claim 1, wherein the secondmask layer over the first top surface of the first mask layer is thickerthan the second mask layer over the inner wall, and the second masklayer over the inner wall is thicker than the second mask layer over thebottom surface.
 9. The method for forming the semiconductor devicestructure as claimed in claim 1, wherein the first mask layer and thesecond mask layer are made of a same material.
 10. The method forforming the semiconductor device structure as claimed in claim 9,wherein the dielectric layer and the first mask layer are made ofdifferent materials.
 11. A method for forming a semiconductor devicestructure, comprising: forming a first mask layer over a dielectriclayer, wherein the first mask layer has a first trench and a secondtrench, and the first trench has a first inner wall and a first bottomsurface; forming a second mask layer over the first inner wall, whereinthe second mask layer has a third trench in the first trench andexposing the first bottom surface, the third trench is narrower than thesecond trench, and the third trench and the second trench arerespectively over a first portion and a second portion of the dielectriclayer; forming an anti-bombardment layer over a first top surface of thefirst mask layer and a second top surface of the second mask layer,wherein the second mask layer and the anti-bombardment layer are made ofdifferent materials; removing the first portion, the second portion, thefirst mask layer, the second mask layer, and the anti-bombardment layerto form a fourth trench and a fifth trench in the dielectric layer,wherein the fourth trench is narrower than the fifth trench; and forminga first conductive structure and a second conductive structurerespectively in the fourth trench and the fifth trench.
 12. The methodfor forming the semiconductor device structure as claimed in claim 11,further comprising: before forming the first mask layer, forming a thirdmask layer over the dielectric layer, wherein the first mask layer isformed over the third mask layer, the second trench and the third trenchrespectively expose a third portion and a fourth portion of the thirdmask layer, and wherein the removing of the first portion, the secondportion, the first mask layer, the second mask layer, and theanti-bombardment layer further comprises: removing the third portion andthe fourth portion.
 13. The method for forming the semiconductor devicestructure as claimed in claim 12, wherein the forming of the firstconductive structure and the second conductive structure comprises:after removing the first portion, the second portion, the third portion,the fourth portion, the first mask layer, the second mask layer, and theanti-bombardment layer, forming a conductive material layer over thethird mask layer and the dielectric layer, wherein the fourth trench andthe fifth trench are filled with the conductive material layer; andremoving the third mask layer and the conductive material layer outsideof the fourth trench and the fifth trench.
 14. The method for formingthe semiconductor device structure as claimed in claim 12, wherein thethird mask layer and the first mask layer are made of differentmaterials.
 15. The method for forming the semiconductor device structureas claimed in claim 12, wherein the third mask layer has a fifth portionand a sixth portion, the fifth portion is covered by the second masklayer, the sixth portion is covered by the first mask layer and is notcovered by the second mask layer, and the sixth portion is thinner thanthe fifth portion after removing the first portion, the second portion,the first mask layer, the second mask layer, and the anti-bombardmentlayer.
 16. A method for forming a semiconductor device structure,comprising: forming a first mask layer over a dielectric layer, whereinthe first mask layer has a first trench and a second trench, and thefirst trench has an inner wall and a bottom surface; forming a secondmask layer over a first portion of a top surface of the first mask layerand the inner wall, wherein the second mask layer exposes a secondportion of the top surface, the first portion and the second portion arerespectively adjacent to the first trench and the second trench, thesecond mask layer has a third trench in the first trench and exposingthe bottom surface, and the third trench and the second trench arerespectively over a third portion and a fourth portion of the dielectriclayer; removing the third portion, the fourth portion, the first masklayer, and the second mask layer to form a fourth trench and a fifthtrench in the dielectric layer, wherein the fourth trench is narrowerthan the fifth trench; and forming a first conductive structure and asecond conductive structure respectively in the fourth trench and thefifth trench.
 17. The method for forming the semiconductor devicestructure as claimed in claim 16, wherein a thickness of the second masklayer over the inner wall increases in a direction away from thedielectric layer.
 18. The method for forming the semiconductor devicestructure as claimed in claim 17, wherein the second mask layer coveringthe first portion of the top surface is thicker than the second masklayer covering the inner wall.
 19. The method for forming thesemiconductor device structure as claimed in claim 16, furthercomprising: before the forming of the second mask layer over the firstportion of the top surface of the first mask layer and the inner wall,conformally forming a third mask layer over the top surface and theinner wall, the second mask layer is formed over the third mask layer,and the removing of the third portion, the fourth portion, the firstmask layer, and the second mask layer further comprises removing thethird mask layer.
 20. The method for forming the semiconductor devicestructure as claimed in claim 19, wherein the second mask layer and thethird mask layer are made of different materials.